A lot of machine shops, and this is my preferred method for stock type street engines, they hone the factory guides to accept new valves with .005 or larger stems. This way you retain the cast iron guides for the street, they last longer.The problem with rebuilding heads is that the integral valve guides have to be bored out, and new guides installed most of the time, on high mileage heads. That can be expensive.
I've done it myself on a Bridgeport mill, and have had it done at a machine shop. New heads wont be much more than having the old ones rebuilt, and newer heads will likely have better characteristics than the old stuff.
Consider what he said ^If you are trying to get performance out of a 305...you could spend you money better by changing the rear gear and then putting in an overdrive transmission... there is nothing really wrong with the 305 but making it make decent power is expensive but a simple gear change and transmission can make it feel like you added a second motor. I put a 3.42 gear and a th2004r in my 83 ---it is by no means a drag machine yet but it is now very respectable to drive around at least ---it was a total dog before, and I have 510 inches of fire breathing engine in the works for it now.
only one problem with that is i have the 267..... its so slowIf you are trying to get performance out of a 305...you could spend you money better by changing the rear gear and then putting in an overdrive transmission... there is nothing really wrong with the 305 but making it make decent power is expensive but a simple gear change and transmission can make it feel like you added a second motor. I put a 3.42 gear and a th2004r in my 83 ---it is by no means a drag machine yet but it is now very respectable to drive around at least ---it was a total dog before, and I have 510 inches of fire breathing engine in the works for it now.